In recent years, an individual identification technology using wireless communication through an electromagnetic field, an electric wave, or the like has attracted attention. In particular, as a semiconductor device that communicates data by wireless communication, an individual identification technology using an RFID (Radio Frequency Identification) tag has attracted attention. An RFID tag (hereinafter, simply referred to as an RFID) is also referred to as an IC (Integrated Circuit) tag, an IC chip, an RF tag, a wireless tag, or an electronic tag. The individual identification technology using an RFID has started to help production, management, or the like of an individual object and has been expected to be applied to personal authentication.
RFIDs can be divided into two types: an active-type RFID and a passive-type RFID, depending on whether it incorporates a power supply or it is supplied with electric power externally. An active-type RFID is disclosed in Reference 1, and a passive-type RFID is disclosed in Reference 2. An active-type RFID incorporates a power supply for driving the RFID and includes a cell as the power supply. In a passive-type RFID, an electric power for driving the RFID is made using an electric wave or electromagnetic wave (carrier wave) externally, and a structure in which a cell is not provided is realized.
FIG. 26 is a block diagram showing a specific structure of an active-type RFID. In an active-type RFID 1400 of FIG. 26, a communication signal received by an antenna circuit 1401 is input to a demodulation circuit 1405 and an amplifier 1406 in a signal processing circuit 1402. The communication signal is normally transmitted after processing such as ASK modulation or PSK modulation is performed on carriers of 13.56 MHz, 915 MHz, or the like. Here in FIG. 26, an example of a case of 13.56 MHz as a communication signal is shown.
In FIG. 26, a clock signal as a reference is needed in order to process signals. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier 1406 and then supplied to a logic circuit 1407 as a clock. Further, the communication signal that is ASK modulated or PSK modulated is demodulated in the demodulation circuit 1405. The demodulated signal is also transmitted to the logic circuit 1407 and analyzed. The signal analyzed in the logic circuit 1407 is transmitted to a memory control circuit 1408, and based on the signal, the memory control circuit 1408 controls a memory circuit 1409 and retrieves data stored in the memory circuit 1409 to transmit the data to a logic circuit 1410. The data transmitted from the memory circuit 1409 is encoded by the logic circuit 1410, and subsequently amplified by an amplifier 1411. A modulation circuit 1412 modulates the carrier in accordance with the signal.
An electric power in FIG. 26 is supplied by a cell 1403 provided outside the signal processing circuit 1402 through a power supply circuit 1404. The power supply circuit 1404 supplies an electric power to the amplifier 1406, the demodulation circuit 1405, the logic circuit 1407, the memory control circuit 1408, the memory circuit 1409, the logic circuit 1410, the amplifier 1411, the modulation circuit 1412, and the like. In such a manner, the active type RFID operates.
FIG. 27 shows a block diagram showing a specific structure of a passive-type RFID. In a passive-type RFID 1500 of FIG. 27, a communication signal received by an antenna circuit 1501 is input to a demodulation circuit 1505 and an amplifier 1506 in a signal processing circuit 1502. The communication signal is normally transmitted after processing such as ASK modulation or PSK modulation is performed on carriers of 13.56 MHz, 915 MHz, or the like. In FIG. 27, an example of a case of using 13.56 MHz as a communication signal is shown.
In FIG. 27, a clock signal as a reference is needed in order to process a signal. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier 1506 and then supplied to a logic circuit 1507 as a clock. Further, the communication signal that is ASK modulated or PSK modulated is demodulated in the demodulation circuit 1505. The demodulated signal is also transmitted to the logic circuit 1507 and analyzed. The signal analyzed in the logic circuit 1507 is transmitted to a memory control circuit 1508, and based on the signal, the memory control circuit 1508 controls a memory circuit 1509 and retrieves data stored in the memory circuit 1509 to transmit the data to a logic circuit 1510. The data transmitted from the memory circuit 1509 is encoded by the logic circuit 1510, and subsequently amplified by an amplifier 1511. A modulation circuit 1512 modulates the carrier in accordance with the signal. On the other hand, the communication signal in a rectifier circuit 1503 is rectified and input to a power supply circuit 1504. The power supply circuit 1504 supplies an electric power to the amplifier 1506, the demodulation circuit 1505, the logic circuit 1507, the memory control circuit 1508, the memory circuit 1509, the logic circuit 1510, the amplifier 1511, the modulation circuit 1512, and the like. In such a manner, the passive-type RFID operates.
[Reference 1]
    Japanese Published Patent Application No. 2005-316724[Reference 2]    Japanese Translation of PCT International Application No. 2006-503376